1. Field of the Invention
The present invention relates to a nanocomposite material and a method of manufacturing the same. More particularly the present invention relates to a nanocomposite material whose internal defects are reduced or eliminated and light stability is enhanced, and a method of manufacturing the same.
2. Description of the Related Art
An example of a nanocomposite is a composite material in which nanoparticles such as quantum dots are densely arranged within a light-transparent matrix material consisting of a metal oxide or a polymer material.
Ligand-exchange processes have been used to manufacture such a nanocomposite material. In particular, a surface ligand of an organic molecule that is chemically coordinated on the surface of the quantum dots obtained by a wet chemical process is exchanged with a hydrophilic ligand having high affinity for a polar solvent such as water or an alcohol. For example, an organic compound such as 4-methylaminopyridine (DMAP) or another polymeric compound is added and the surface ligand of an organic molecule is exchanged with a hydrophilic ligand. Then the quantum dots, whose surfaces are modified, are mixed in a precursor solution, and the mixture is subjected to a sol-gel reaction and then a drying process, thereby obtaining a nanocomposite material impregnated with the quantum dots as a hardened solid.
FIGS. 1A and 1B are photographs of an existing nanocomposite material during the drying process, in which cracks grow when the nanocomposite material is being dried due to a non-symmetrical drying rate between the surface and the inner body of the nanocomposite, which eventually cracks into pieces. The binding strength and affinity between a matrix material and quantum dots impregnated therein is so insufficient that cracks occur frequently in the nanocomposite material as the solvent in the sol phase is evaporated during the drying process. Such cracks formed in the nanocomposite material, for example, reduce the efficiency for extracting light, provide a penetrating path for harmful materials such as oxygen/moisture thereby reducing the emitting property of the nanoparticles, and decrease the durability of the nanocomposite material.
To address these problems, the drying process can be somewhat delayed by adding a drying releasing agent such as dimethylformamide (DMF) to a precursor solution of the matrix. However, for such a method, impurities are inevitably incorporated into the nanocomposite material, and disruptive behavior can be induced in the nanocomposite material as the extra releasing agent is evaporated.